1. Field of the Invention
This invention relates to the field of fabricating molds polymeric items, and more specifically, to an automated system for the post-processing of polymeric molds, particularly molds for fabricating plastic orthodontic appliances.
2. Background
Stereolithography is a rapid prototyping process used to create solid, plastic, three-dimensional (3-D) objects, such as molds, from CAD drawings. For example, stereolithography is used to fabricate molds that are used to make plastic orthodontic alignment appliances, as described, for example, in U.S. Pat. No. 5,975,893 and US Patent Application Publication 2005/0082703, both of which are commonly assigned to the assignee of the subject invention, and the disclosures of which are both incorporated herein by reference.
Plastic orthodontic appliances, of the type disclosed in the above-referenced documents, are made as a set of incremental position adjustment appliances that are used to realign or reposition a patient's teeth. The series of incremental position adjustment appliances is custom made for each patient during the fabrication process.
The fabrication process starts with a dentist making impressions or casts of the upper and lower dental arches of a patient. The impressions or casts are then sent by the dentist to an orthodontic appliance manufacturing facility. The manufacturing facility creates a treatment file from the impressions or casts that includes the treatment information for the patient. Treatment information includes the number of stages (i.e. each appliance in the series of incremental position adjustment appliances represents a stage) for both the upper and lower dental arches that are required for repositioning the patient's teeth, as well as how the patient's teeth move during each stage. The treatment file is then sent to the dentist for approval. Upon approval, the manufacturing facility generates 3D CAD models or images of molds for making the appliances using the treatment file, and then creates the molds using a rapid prototyping process, such as, for example, stereolithography. The molds are then used to fabricate the appliances.
Once the molds have been created, the molds are subjected to several post-processing steps. Currently, the post-processing of the molds is done manually, and includes removing any debris and any excess mold material (i.e., polymeric resin) from the molds. To clean the molds, they are first soaked in a solvent, and then they are sprayed with water and air to remove the excess resin and the loosened debris, and to rinse off the solvent.
The solvent used to clean the molds is toxic to the environment, and using fresh water to rinse off the solvent results in a significant consumption of water. Additionally, manually cleaning the molds is labor-intensive, and therefore entails substantial costs and time to produce the items. Accordingly, there is a need for an efficient system and method to improve productivity by automating the post-processing of the molds, using only water to clean the molds, and purifying the used water and waste resin from the molds to be reused.